leetcode

1 Random Problem

2 files changed, 43 insertions(+), 0 deletions(-)

diff --git a/ Problems/1911.cpp b/ Problems/1911.cpp

@@ -0,0 +1,42 @@

// Standard dp

class Solution {

static long long dp[2][100001];

long long rec(const vector<int> &nums, const int crnt, const bool odd) {

if (crnt >= size(nums)) return 0;

if (dp[odd][crnt] != -1) return dp[odd][crnt];

long long res =

max(rec(nums, crnt + 1, odd), (odd ? -1 : 1) * nums[crnt] + rec(nums, crnt + 1, !odd));

return dp[odd][crnt] = res;

}

public:

Solution() { memset(dp, 0xFF, sizeof(dp)); }

long long maxAlternatingSum(const vector<int> &nums) { return rec(nums, 0, 0); }

};

long long Solution::dp[2][100001];

// Optimized 1

class Solution {

public:

long long maxAlternatingSum(const vector<int> &nums) const {

long long odd = 0, even = 0;

for (const int n : nums) {

even = max(even, odd + n), odd = even - n;

}

return even;

}

};

// Optimized 2

class Solution {

public:

long long maxAlternatingSum(const vector<int> &nums) const {

long long res = nums[0];

for (int i = 1; i < size(nums); i++) {

res += max(nums[i] - nums[i - 1], 0);

}

return res;

}

};

diff --git a/ README.md b/ README.md

@@ -874,6 +874,7 @@ for solving problems. | 1905 | Medium | [Count Sub Islands](Problems/1905.cpp) | | 1907 | Medium | [Count Salary Categories](Problems/1907.cpp) | | 1910 | Medium | [Remove All Occurrences of a Substring](Problems/1910.cpp) |

| 1911 | Medium | [Maximum Alternating Subsequence Sum](Problems/1911.cpp) |

| 1913 | Easy | [Maximum Product Difference Between Two Pairs](Problems/1913.cpp) | | 1921 | Medium | [Eliminate Maximum Number of Monsters](Problems/1921.cpp) | | 1926 | Medium | [Nearest Exit from Entrance in Maze](Problems/1926.cpp) |